Road Bikes - Why no hydraulics?

[MartinC]

Thinking about it, why would disc forks have to be stronger than road forks?

Rim brakes apply the braking force directly at the fork crown. This is an inherently strong part of the fork.

Disk brakes apply a rotational force at the tips of the fork blades. Fork blades are normally designed to be stiff in relation to lateral forces but allow some vertical compliance for comfort. To resist the reaction force from braking at the hub they need to be beefed up (in relation to a fork for rim brakes in the same bike) to resist the extra force. This makes them heavier and less comfortable and is one of the reasons (and one of the less significant ones) that they aren't likely to appear on racing bikes.

 

[gaz]

I wonder how many TDF riders thrashing down 100kph descents realise just how weak their bikes are!

Their bikes aren't weak.
The carbon forks used on racing bikes are not designed to cope with the forces a disc brake provides at end of the fork.

 

[Piemaster]

Rim brakes apply the braking force directly at the fork crown. This is an inherently strong part of the fork.

Disk brakes apply a rotational force at the tips of the fork blades. Fork blades are normally designed to be stiff in relation to lateral forces but allow some vertical compliance for comfort. To resist the reaction force from braking at the hub they need to be beefed up (in relation to a fork for rim brakes in the same bike) to resist the extra force. This makes them heavier and less comfortable and is one of the reasons (and one of the less significant ones) that they aren't likely to appear on racing bikes.

Wouldn't disagree with that, however as I posted no matter where the brakes are applied the force on the lever (the fork) is between the fork crown and the road/tyre interface, regardless of the type of brake.
Both types of brakes at a basic level work the same - clamping a rotating metal disc between two brake pads - the only difference is the distance at which they operate from the hub, around 12" difference on a 700c wheel. Sat watching the TdF at the moment I can't believe the aero forks (thin section but wide longitudinally) that are in use would struggle with any rotational forces applied to them by a disc brake at 80mm from the hub (160mm rotor/2)
We are talking about road use bikes as well, not offroad use, the fork does not have to be capable of being jumped. I don't think the 'disc brakes go on mtb so has to be heavy duty' mindset has been gotten away from yet.

Of course the aero shape of the fork and positioning of road calipers for less drag probably makes more sense for Tour riders than me. And they do look better

 

[Cubist]

Discs on road bikes are just wrong. Simple. Ugly - ugly things are not allowed on road bikes !

Ideal though for crappy conditions - would be great on a commuter. I tend to eat rims on my fixed. I get about 18-24 months out of a rim.

How could you possibly describe these as ugly?

 

[xpc316e]

Their bikes aren't weak.
The carbon forks used on racing bikes are not designed to cope with the forces a disc brake provides at end of the fork.

Cubist's comment was, I suspect intended to be an example of irony. The big smiley at the end, and his remarks about 100kph descents, are meant to make us think that the bikes are massively strong.

 

[xpc316e]

I have four bikes; they use Ultegra calipers, Avid V brakes, Quad hydraulic discs, and Avid cable discs. I would choose the hydraulic discs on any, and every occasion. The cable discs come in in second place, with the honours about equal between the last two. I'd buy a road bike equipped with hydraulic discs like a shot, and I reckon that anybody would make the same choice if they had experience of that type of brake. I used to have a bike with Magura hydraulic rim brakes, and they were good but not a patch on discs. Hopefully, the powers that be will drag themselves into the 21st century and allow discs in competition, then fashion will bring them onto 'road' bikes.

 

[Piemaster]

Hopefully, the powers that be will drag themselves into the 21st century and allow discs in competition, then fashion will bring them onto 'road' bikes.

Slippery slope from there though, they'll be letting them funny recumbent things in competition before you know it

 

[MacB]

I have four bikes; they use Ultegra calipers, Avid V brakes, Quad hydraulic discs, and Avid cable discs. I would choose the hydraulic discs on any, and every occasion. The cable discs come in in second place, with the honours about equal between the last two. I'd buy a road bike equipped with hydraulic discs like a shot, and I reckon that anybody would make the same choice if they had experience of that type of brake. I used to have a bike with Magura hydraulic rim brakes, and they were good but not a patch on discs. Hopefully, the powers that be will drag themselves into the 21st century and allow discs in competition, then fashion will bring them onto 'road' bikes.

That last bit is where I wouldn't hold my breath, the advantages of discs that many of us perceive just don't really exist in racing, or at least not at the top level. If your bike was checked daily by a professional mechanic and new bits constantly added I suspect you'd find rim brakes perfectly ok. They have no considerations around pad wear, rim wear and wheel truing.

Unless the change happens at pro level then it won't happen further down as people wouldn't want to get used to one braking system only to ride an entirely different one once they 'make it'. If the marketing folks see money in it then it might go ahead though.

 

[MartinC]

Wouldn't disagree with that, however as I posted no matter where the brakes are applied the force on the lever (the fork) is between the fork crown and the road/tyre interface, regardless of the type of brake.
Both types of brakes at a basic level work the same - clamping a rotating metal disc between two brake pads - the only difference is the distance at which they operate from the hub, around 12" difference on a 700c wheel. Sat watching the TdF at the moment I can't believe the aero forks (thin section but wide longitudinally) that are in use would struggle with any rotational forces applied to them by a disc brake at 80mm from the hub (160mm rotor/2)

Your model is too simple. Rim brakes operate by clamping the rim which is taking the force generated by the tyre on the road. The braking force is transmitted to the bike throught the fork crown - the fork blades are only partially involved. A disk brake is applying the force at the wheel spindle, the fork tip has to take the reaction force from the clamped rotor - this is why they there was a tendency to pop front wheels out when the caliper was on the wrong side of the fork.

The OP was about hydraulics but this has strayed into a discussion about rim v. disk. Disks are a very effective solution for MTB's and Hybrids (in whatever the widest sense is) but they aren't going to appear on race bikes because of thermal efficiency, aerodynamics and because the current solution works as effectively as is required - you can easily lock a wheel already so no extra braking power can help. Apart from some issues with modulation on carbon braking surfaces there isn't a driver to change other than the perennial desire to get rid of drag and weight.

 

[steve52]

some one with some savy ie not me set up a poll vote thingy, disks on road bikes or not? i for one want to see them

 

[Alun]

http://www.flickr.co.../in/photostream

What chainset do you have on the Burls, MacB? The inner chainwheel looks tiny, how many teeth does it have?

Sorry to be off topic, but I'm intrigued.

Cheers

 

[amaferanga]

That last bit is where I wouldn't hold my breath, the advantages of discs that many of us perceive just don't really exist in racing, or at least not at the top level. If your bike was checked daily by a professional mechanic and new bits constantly added I suspect you'd find rim brakes perfectly ok. They have no considerations around pad wear, rim wear and wheel truing.

Unless the change happens at pro level then it won't happen further down as people wouldn't want to get used to one braking system only to ride an entirely different one once they 'make it'. If the marketing folks see money in it then it might go ahead though.

Given that most pros use full carbon rims and therefore have relatively poor braking at the best of times (braking on carbon rims is snatchy) and scary (lack of) braking in the wet, I'd say that there could potentially be an advantage in racing at the top level.

If they can actually work on a road bike without adding too much weight then they would IMO be an improvement.

 

[MacB]

What chainset do you have on the Burls, MacB? The inner chainwheel looks tiny, how many teeth does it have?

Sorry to be off topic, but I'm intrigued.

Cheers

it's a stronglight 46/36/26 but I changed the 26 to a 24t, in my current condition it's used, when fit I expect the 24t won't see a lot of action, but I like knowing it's there.

 

[MacB]

Given that most pros use full carbon rims and therefore have relatively poor braking at the best of times (braking on carbon rims is snatchy) and scary (lack of) braking in the wet, I'd say that there could potentially be an advantage in racing at the top level.

If they can actually work on a road bike without adding too much weight then they would IMO be an improvement.

ah, heard a few remarks along those lines on the TdF commentary, but I have no experience of carbon rims. If the above is the case then I can see an impetus for change that I didn't before.

I'm sure I saw one concept bike that had two calipers and rotors on the front to even out braking forces, but not heard anything of it since.

 

[2Loose]

It is too easy to skid narrow tyres using rim brakes as it is, they just do not have a large enough road contact point to require any more braking power.

I can hammer my fat tyred bikes brakes and not skid, but on the roadie, braking forces even close to that end up with wheel slip as the tyre loses traction with the road.

I love disks for the wet weather braking and being kinder to rims throughout winter, but thin tyres can't really handle any more power than calipers already provide.